Projectors are generally devices that integrate light sources, optics systems, electronics, and displays for projecting images from computers or video devices onto walls or screens, for large-image viewing. They are especially popular among business users who give presentations as part of their job responsibilities. Newer projectors can weigh as little as a few pounds, making them well suited for business travelers. As the quality of projection technology has improved, projectors are also finding their way into peoples' homes for high-definition television (HDTV) and other home entertainment applications. Some industry pundits predict that digital projectors will also become the standard projection technology used in movie theaters.
The light sources utilized in projectors are an integral factor in the resulting quality of the projected image. A light source is desirably small in size, long lasting, and uniform in the light that it produces. Until recently, most projectors relied on metal halide lamps that employ a spark across a gas-filled gap to create light. However, metal halide lamps tended to have color and luminance stability problems, and tended to deposit materials on their sidewalls during operation, resulting in reduced brightness. More recently, some projectors have been using ultra high pressure (UHP) arc lamps. These lamps use an arc in a pure mercury vapor under high pressure. The arc gap is much smaller than the gas-filled gap of a metal halide lamp, resulting in greater lighting efficiency. Small amounts of oxygen and halogen are usually mixed with the mercury vapor, helping to remove material deposits from a lamp's sidewalls, which maintains the lamp's brightness substantially throughout its lifetime.
However, UHP mercury-vapor arc lamps, as well as other types of lamps used in projectors, still suffer from some drawbacks. Arc lamps, for instance, usually output less light at red wavelengths than they do at other wavelengths. This means that parts of the images being projected that rely on red wavelengths of light for rendering may not appear as bright, or may appear inaccurate as compared to how they should appear. Arc lamps may also have uneven color intensities. For instance, the light output at blue wavelengths, or at green wavelengths, may only be able to be produced at deep or dull tones. This means that parts of the images being projected that rely on these wavelengths of light for rendering may appear dull, or may also appear inaccurate as compared to how they should appear.
For these and other reasons, therefore, there is a need for the present invention.